Real-World Cryptography

I would suggest Real-World Cryptography by DAVID WONG. It has good introduction covering basic primitives like various hash functions, MAC, KDF, then sym/asym, and so on, all the way to PQC and protocols design. A nice intro book, maybe your 10 y.o. will find it interesting. P.S. In fact, I was going to send that book to my friend's son who is about same age, and who got some sudden interest in cryptography recently. So it is safe to say that I am now aware of at least two 10 year olds who have interest in Cryptography. I feel a bit surprised, but in a good way :)